The ligament of the head of the femur was studied by dissection in 40 human cadavers, 5 monkeys, 10 cats and 20 rats over a two-year period. Unlike the situation in the monkeys, cats and rats studied, the ligament was not invariably present in humans. It was absent in 4 of the cadavers studied. In 3 of them, the ligament was absent unilaterally. In the remaining 36 cadavers, the ligament was strong in 26 cadavers, weak in 9 and was torn in one. The present findings suggest that although the ligament transmits an artery to the femoral head in the young, it does not appear to have any important mechanised function in maintaining the stability of the hip joint.